Size distribution of a drop undergoing breakup at moderate Weber numbers*

We investigate the size distribution of child droplets resulting from dual-bag fragmentation of a water drop using shadowgraphy and digital in-line holography. Our observations show that while parent drop fragmentation mainly produces tiny droplets, core drop disintegration yields larger fragments. Despite the complexities of dual-bag fragmentation, it results in a bi-modal size distribution, unlike single-bag breakup, which shows a tri-modal distribution. We employ an analytical model for dual-bag fragmentation, which effectively predicts the experimentally observed droplet volume probability density. Additionally, we estimate the temporal evolution of child droplet production to illustrate the decomposition into initial and core breakups quantitatively. Our analysis confirms that the model accurately predicts the droplet size distribution across a range of Weber numbers.